Transfer printing apparatus of electrophotographic apparatus

ABSTRACT

In transfer printing apparatus of electrophotographic apparatus of the type wherein a receptor sheet is urged against a photosensitive element carried by a rotary drum by means of a transfer printing roller so as to transfer print an electrostatic latent image formed on the photosensitive element. Preferably, the separating member comprises a pair of strips which are disposed at an angle with respect to the direction of movement of the receptor sheet. Onto the receptor sheet there is provided a stationary separating member between the receptor sheet and the photosensitive element.

United States Patent Suzuki et al.

[451 Oct. 29, 1974 TRANSFER PRINTING APPARATUS OF ELECTROPHOTOGRAPHIC APPARATUS Inventors: Ryuzo Suzuki, Tokyo; Seiichi Miyakawa, Nagareyama; Masanori Watanabe, Tokyo, all of Japan Katsuragawa Denki Kabushiki Kaisha, Tokyo-to, Japan Filed: Jan. 16, 1974 Appl. No.: 433,713

Assignee:

Foreign Application Priority Data July 28, 1971 Japan 57078/46 July 28, 1971 Japan 57079/46 Related UQS. Aspiration Data Division of Ser. No. 273,425, July 20, 1972.

US. Cl. 355/3, 355/108 Int. Cl G03g 15/16 Field of Search 355/3, 103, 108

References Cited UNITED STATES PATENTS 12/1962 Eisbein 355/103 X FOREIGN PATENTS OR APPLICATIONS 1,175,079 7/1964 Germany Primary Examine r -John M. Horan Attorney, Agent, or Firm-Bosworth, Sessions & McCoy [5 7] ABSTRACT In transfer printing apparatus of electrophotographic apparatus of the type wherein a receptor sheet is urged against a photosensitive element carried by a rotary drum by means of a transfer printing roller so as to transfer print an electrostatic latent image formed on the photosensitive element. Preferably, the separating member comprises a pair of strips which are disposed at an angle with respect to the direction of movement of the receptor sheet. Onto the receptor sheet there is provided a stationary separating member between the receptor sheet and the photosensitive element.

6 Claims, 6 Drawing Figures TRANSFER PRINTING APPARATUS OF ELECTROPHOTOGRAPHIC APPARATUS This is a division, of application Ser. No. 273,425 filed July 20, I972.

BACKGROUND OF THE INVENTION This invention relates to apparatus for separating a receptor sheet or a transfer printing paper from a photosensitive drum of an electrophotographic apparatus after an electrostatic latent image formed on the surface of the drum has been transfer printed onto the receptor sheet.

In one type of electrophotographic apparatus, an electrostatic latent image formed on the surface of a rotary photosensitive element corresponding to an original is transfer printed onto a receptor sheet by means of a transfer printing roller which acts to urge the receptor sheet against the photosensitive element and then the transfer printed latent image is developed to obtain a visible image. However, it is difficult to separate or peel off the receptor sheet from the photosensitive element because the electrostatic force of the latent image attracts the receptor sheet toward the photosensitive element.

To positively separate the receptor sheet from the photosensitive element it has been proposed various devices including l) a device wherein a peel off member is contacted against the periphery of the rotary photosensitive element for mechanically separating the receptor sheet. (2) a device wherein the leading edge of the receptor sheet is slightly curved away from the periphery of the photosensitive element and a peel off member is disposed with its inner end slightly spaced apart from the periphery of the rotary photosensitive element so as not to damage it, (3) a device wherein after the transfer printing an air jet is applied to the leading edge of the receptor sheet to separate it from the'photosensitive element, (4) a device wherein a suction drum is arranged behind the receptor sheet to separate it by suction, (5) and combinations of these devices. However. with devices (l and (2) it is impossible to transfer print the latent image along the entire length of the receptor sheet thus decreasing the effective area thereof. Devices (3) and (4) not only require the provision of a source of pressurized air but also are difficult to positively peel off the receptor sheet where the quantity of the charge of the latent image is large asin the case of a perfectly black picture.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a new and improved apparatus for separating a receptor sheet from a photosensitive element.

Another object of this invention is to provide novel separating apparatus of simple construction which can efficiently separate a receptor sheet from a rotary photosensitive element after the electrostatic latent image has been transfer printed but does not interfere with the transfer printing.

According to this invention there is provided transfer printing apparatus of electrophotographic apparatus of the type wherein a receptor sheet is urged against a photosensitive element carried by a rotary drum by means of a transfer printing roller so as to transfer print an electrostatic latent image formed on the photosensitive element onto the receptor sheet, characterized in that a stationary supporting member is interposed between the receptor sheet and the photosensitive element.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. I shows a side view, partly broken away, of a photosensitive drum provided with separating apparatus embodying the invention;

FIG. 2 is a plan view of a transfer printing roller and separating members;

FIG. 3 shows a side view similar to FIG. 1 but show ing a modified embodiment using two transfer printing rollers;

FIG. 4 is a plan view showing the transfer printing roller and separating members of the embodiment shown in FIG. 3;

FIG. 5 is a plan view similar to FIG. 4 showing moditied transfer printing rollers and FIG. 6 is a plan view showing a modified separating member and modified transfer printing rollers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I, a rotary photosensitive drum l0 utilized for forming an electrostatic latent image on the periphery thereof may be any suitable construction and the latent image may be formed by any suitable method. In the illustrated example, the drum 10 carries a cylindrical photosensitive element 11 including an electrode layer 14, a photoconductive layer 13 and a transparent highly insulative layer 12 which are bonded'together into an integral cylindrical structure. Where the drum 10 is made of metal, the electrode layer 14 may be omitted. The photoconductive layer 13 may be made of any photoconductive material or phosphor manifesting persistent internal polarization, such as CdS, Zn CdS, CdS or Zn CdS activated with copper or silver, selemium, anthracene or TeSe. A latent image may be formed on the surface of the highly insulative layer 12 by applying a first electric field across the photosensitive element to deposit a charge of one polarity on the surface of the highly insulative layer thereby establishing substantially uniform persistent internal polarization in the photoconductive layer, applying a second electric field across the photosensitive element to deposit a charge of the opposite polarity on the surface of the highly insulative layer, and pro jecting a light image upon the photoconductive layer through the highly insulative layer concurrently with the application of the second electric field thereby forming the latent image on the surface of the highly insulative layer. Above described method is advantageous in that the latent image is not erased by later irradiation of light so that it is possible to carry out the transfer printing and developing operations in the bright. Where the photoconductive layer contains a large number of deep charge trap levels, as in the case of Zn CdS activated with silver or copper, it is desirable to irradiate the letent image with uniform light from an electric lamp for example.

In the case of the conventional xerography, the latent image is formed. by applying an electric field across'the photosensitive element in the dark and then projecting a light image. In this case, however, as the latent image is readily erased by light it is necessary to carry out the transfer printing and developing operations in the dark as is well known in the art.

To transfer print the latent image thus formed on the periphery of the photosensitive element onto a receptor sheet P, usually an ordinary paper, there is provided a transfer printing roller 15 which is made of rubber, for example, and is urged against the periphery of the rotary photosensitive element 11 by suitable means, not shown. According to this invention, one, two or more spaced apart separating members 16 of a fiber, string or tape of a synthetic resin such as nylon and polytetrafluoroethylene or metal foil are provided between stationary members 17, to extend through the nip between photosensitive element 11 and transfer printing roller 15 and the receptor sheet P is fed between the separating members and the transfer printing roller. Among various materials, strips of polytetrafluoroethylene are found to be most suitable because they have flat and smooth surface so that they do not damage the photosensitive element and receptor sheet by the contact friction, and because they have small elongation, a large shear strength and a long life. Even when a conductive material such as a metal foil or sheet is used, the electrostatic latent image would not be erased so long as the contact pressure between the separating members and the photosensitive element is low. Conductive material has a large durability. As shown in FIG. 2, the separating members are disposed at an angle 9 with respect to the direction of movement of the receptor sheet P which is indicated by arrow A. Since the separating members are disposed between the rotary drum and the receptor sheet they act to separate the receptor sheet from the rotary drum after transfer printing. As the rotary drum is rotated, the separating members are contacted by the surface of the photosensitive element so that one may consider that the latent image would be erased or certain portion of the latent image would not be transfer printed. Actu' ally, however, it was found that the latent image can be satisfactorily transfer printed where a relation a/W sin is satisfied, where W represents the contact width between the peripheries of the photosensitive element and transfer printing roller and a the width of a separating member. Moreover, since the separting members are disposed at an angle with respect to the direction of movement of the receptor sheet P it is possible to prevent the receptor sheet from crimpling. While separating members of any number may be used, the material from which the separating members are formed should be wear resistant and should not damage the surfaces of the photosensitive element and the receptor sheet. The result ofexperiment shows that a nylon fiber having a diameter of 0.2 mm and a tape of polytetrafluoroethylene having a thickness of 0.05 mm and a width of 3 mm are satisfactory. The separation of the receptor sheet can be enhanced where the receptor sheet P is fed into the nip and removed from the nip, both at an angle with respect to the separating members, as diagramamatically shown in FIG. 1. Further, the separating members maybe inclined in the same direction, but better results are obtained when they are inclined in the opposite directions as shown in FIG. 2.

In the modified embodiment shown in FIGS. 3 and 4, two parallel transfer printing rollers a and 15b which are spaced apart in the direction of movement A of the receptor sheet are provided to increase the effective area of the contact width W. With this arrangement there is no fear of mis-transfer printingeven when the width a of the separating members 16 is large. More particularly, as shown in FIG. 4, when the latent image is transfer printed by transfer printing roller 151;, the portions of the latent image corresponding to widths c may not be effectively transfer printed by the interference of the separating members 16. However, these portions are not interferred by the separating members 16 while the latent image is transfer printed by the other transfer printing roller 15a.

In another embodiment shown in FIG. 5, the transfer printing rollers 15a and 15b are provided with reduced diameter portions 18 which receive separating members 16 so as not urge them against the periphery of the photosensitive element.

In the modification shown in FIG. 6, the separating member 19 takes the form of a web of a synthetic resin. In this case, transfer printing roller 15b is formed with a reduced diameter portion 18 at the middle section thereof, whereas the other transfer printing roller 15a is provided with reduced diamter portions 18 on the opposite end sections. The separating member 19 is provided with windows 20b and 20a at the larger diameter protions of the transfer printing rollers 15b and 15a, respectively. Windows 20a and 20b are staggered in the lateral direction with respect to the direction of movement of the receptor sheet. Thus, the entire width of the receptor sheet interposed between the transfer printing rollers and the separating member is urged against the periphery of the photosensitive element to effect efficient transfer printing of the latent image.

According to the embodiments shown in FIGS. 5 and 6, since the separating member is not urged against the periphery of the photosensitive element by the provision of reduced diameter portions 18 there is no fear of damaging by friction the surface of the photosensitive element and the latent image which has been transfer printed on the surface of the receptor sheet.

While the invention has been shown and described in connection with a particular method of forming an electrostatic latent image, it will be clear that the latent image can be formed by any method and by utilizing any one of many known photosensitive elements. If desired, suitable voltage may be applied between the rotary drum and the transfer roller to enhance transfer printing.

We claim:

1. In apparatus for transfer printing of electrophotographic images comprising a rotary drum provided with a photosensitive element on which an electrostatic latent image is to be formed, a transfer printing roller for urging a receptor sheet through the nip between said roller and said photosensitive element and against the surface thereof so as to transfer print said electrostatic latent image onto said receptor sheet, and a separating member for separating said receptor sheet from said photosensitive element after transfer printing, the improvement wherein said separating member comprises a pair of stationary elongated members which are inclined in opposite directions with respect to the direction of movement of said receptor sheet and extend through said nip when the apparatus is in use for moving the receptor sheet relative to the surfaces of said elongated members which face said transfer printing roller and for separating the receptor sheet away from said photosensitive element after the receptor sheet has passed through said nip.

5. The transfer printing apparatus according to claim 1 wherein said stationary separating means comprises a pair of stationary strips which are inclined in opposite directions with respect to the direction of movement of said receptor sheet.

6. ln apparatus for transfer printing of electrophoto- 6 graphic images comprising a rotary drum provided with a photosensitive element on which an electrostatic image is to be formed, a receptor sheet and a transfer printing roller for urging said receptor sheet against the surface of said photosensitive element to transfer print said latent image onto said receptor sheet, the improvement which comprises a pair of stationary separating strips interposed between said receptor sheet and said photosensitive element, each of said stationary strips being disposed at an angle 6 with respect to the direction of movement of said receptor sheet, said angle 0 satisfying a relation 0/ W sin 6 where W represents the contact width between the peripheries of the photosensitive element and the transfer printing roller and a the width of said separating strip.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,844,652 Dated October 29, 1974 Inventofls) Ryuzo Suzuki, Seiichi Mivakawa and Masanori Watanabe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Abstract should read as follows:

--In transfer printing apparatus of ele-ctrophotographic apparatusof the type wherein a receptor sheet is urged against aphotosensitive element carried by arota ry drum' by means of a transfer printing roller so as to transfer print an electrostatic latent image formed on the photosensitive element onto the receptor sheet there is provided a stationary separating member between the receptor 7 sheet and'the' photosensitive element. Preferably, the separating member comprises a pair of strips which are disposed at an angle with respect to the direction of movement of the receptor sheet.

Column 5, lines 12 to 16, claim 5 should read as follows:

-5. A transfer printing apparatus according to claim 1 wherein said elongated members comprise. a pair of stationary strips which are inclined in; opposite directions with respect to the direction 'ofmovement of said receptor sheet and wherein said transfer printing roller is provided with reduced diameter portions for receiving said stationary strips.-

Signed and sealed this 14th day of January 1975. I

(SEAL) Attest: p

. 1- C. MARSHALL DANN Commissioner of Patents FORM 734050 10-69) USCOMM-DC MG-Pee I u i On-nun! nmmu: omcl nu o-au-au UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,844,652 Dated October '29, 1974 Inventor(s) Ryuzo Suzuki, Seiichi Miyakawa and Masanori Watanabe It is certified that error appears in the above-ddentified patent and that said Letters Patent are hereby corrected as shown below:

The Abstract should read as follows:

-In transfer printing apparatus of electrophotographic apparatus of the type wherein a receptor sheet is urged against aphotosensitive element carried by a rotary drum by means of a transfer printing roller so as to transfer print an electrostatic latent image formed on the photosensitive element onto the receptor sheet there is provided a stationary separating member between the receptor sheet and the photosensitive element. Preferably, the separating member comprises a pair of strips which are disposed at an angle with respect to the direction of movement of the receptor sheet.--

Column 5, lines 12 to 16, claim 5 should read as follows:

--5. A transfer printing apparatus according to claim 1 wherein said elongated members comprise. a pair of stationary strips which are inclined in opposite directions with respect to the direction 'of.moveme nt of said receptor sheet and wherein said transfer printing roller is provided with reduced diameter portions for receiving said stationary strips.--'

Signed and sealed this 14th day of January 1975.

(SEAL) Arrest:

0N JR. P C. MARSHhLL DANN zggzs ing ificer Commissioner of Patents FORM ro-mso 110-691 ammo: and, I U i Govt-mar WIIIYIIG O'IICI INI O-dfl-Dl 

1. In apparatus for transfer printing of electrophotographic images comprising a rotary drum provided with a photosensitive element on which an electrostatic latent image is to be formed, a transfer printing roller for urging a receptor sheet through the nip between said roller and said photosensitive element and against the surface thereof so as to transfer print said electrostatic latent image onto said receptor sheet, and a separating member for separating said receptor sheet from said photosensitive element after transfer printing, the improvement wherein said separating member comprises a pair of stationary elongated members which are inclined in opposite directions with respect to the direction of movement of said receptor sheet and extend through said nip when the apparatus is in use for moving the receptor sheet relative to the surfaces of said elongated members which face said transfer printing roller and for separating the receptor sheet away from said photosensitive element after the receptor sheet has passed through said nip.
 2. The transfer printing apparatus according to claim 1 wherein a plurality of transfer printing rollers are provided which are parallel with each other and are spaced apart in the direction of movement of said receptor sheet.
 3. The transfer printing apparatus according to claim 1 wherein said elongated members are made of a synthetic resin.
 4. The transfer printing apparatus according to claim 1 wherein said elongated members are made of metal.
 5. The transfer printing apparatus according to claim 1 wherein said stationary separating means comprises a pair of stationary strips which are inclined in opposite directions with respect to the direction of movement of said receptor sheet.
 6. In apparatus for transfer printing of electrophotographic images comprising a rotary drum provided with a photosensitive element on which an electrostatic image is to be formed, a receptor sheet and a transfer printing roller for urging said receptor sheet against the surface of said photosensitive element to transfer print said latent image onto said receptor sheet, the improvement which comprises a pair of stationary separating strips interposed between said receptor sheet and said photosensitive element, each of said stationary strips being disposed at an angle theta with respect to the direction of mOvement of said receptor sheet, said angle theta satisfying a relation a/W < sin theta where W represents the contact width between the peripheries of the photosensitive element and the transfer printing roller and a the width of said separating strip. 